Allseas

Offshore substation foundation design case

Allseas is a privately owned, world-leading contractor in offshore pipeline installation and heavy lift removal and installation work, with projects all across the globe. Recently, Allseas secured a contract for the installation of an offshore substation for one of the largest windfarms in the North Sea.

This substation will be installed on top of a so-called jacket; a steel framework of roughly 60 m high, extending all the way from the seafloor to 20 m above the waterline. To anchor the jacket to the seafloor, typically large steel foundation piles are hammered through the structure and connected to the jacket. However, the offshore hammering of piles is a noisy and time-consuming process, driving costs, and endangering marine life due to shock waves propagating through the water.

Recently, an alternative, innovative foundation method has been introduced for the anchoring of jackets, using suction pile technology. For this method, the bottom of the jacket is outfitted with several large inverted steel buckets. Once the jacket is positioned on the seafloor, water will be pumped out from the buckets, creating under-pressure in the buckets, effectively sucking them into the soil. This foundation method is less noisy and time consuming, but potentially increases fabrication cost and installation complexity.

You, as a team of starting Heavy Lift Engineers, have been assigned to evaluate these different jacket foundation options, select the best one, and convince the client of the quality of your assessment.

During the case, you will learn the basics of installing structures using Allseas’ record‑breaking vessel Pioneering Spirit, get to challenge yourself and your teammates to find the optimal solution for both Allseas, the client, and the environment, and get a feel for whether you have what it takes to work as an Engineer at Allseas! Good luck!